Cardiff Blues have confirmed that centre Owen Williams has suffered a "significant injury to his cervical vertebrae and spinal cord."
The 22-year-old, who has played four times for Wales, was injured playing for Cardiff Blues at the World Cup 10s on Sunday.
The region said that he underwent an operation on Monday to stabilise a fracture and is currently recovering in hospital in Singapore.
His family and Blues staff are with him in hospital, and arrangements are now being made to arrange his safe transfer home "at an appropriate time."
The region and Williams' family have also thanked hundreds of people who have offered messages of support.
Owen Williams' brother has tweeted his thanks to those offering messages of support, after the 22-year-old Cardiff Blues and Wales centre was injured in Singapore.
Williams' family flew out to be by his side in hospital, after he sustained what is thought to be a serious neck injuries playing in the World Club 10s on Sunday.
Hundreds of messages of support have come in from Wales, and also rugby stars like Australia's David Pocock.
Very little is known about the nature or extent of Owen Williams' injury, sustained whilst playing for Cardiff Blues against Asia Pacific Dragons in the World Club 10s on Sunday.
The Blues released a statement yesterday, saying: "Owen Williams is to remain in hospital in Singapore after sustaining an injury at the World Club 10s. Cardiff Blues will issue further updates when they are available."
Blues teammate Macauley Cook also tweeted yesterday to say he was at the hospital with Williams, waiting for his family to arrive.
The WRU said 22-year-old Williams has not travelled home with the rest of the Blues squad.
Messages of support from around the Welsh rugby community have been posted on Twitter, for Cardiff Blues and Wales centre Owen Williams, who suffered a serious injury at the World Cup 10s in Singapore.
The 22-year-old is believed to still be in hospital in Singapore, after being injured in the tournament on Sunday.
There is very little detail about the nature or extent of his injury.
Goodwill messages have come in this morning from Wales legend Shane Williams, Alun Wyn Jones - who captained the side in South Africa, and Regional Rugby Wales, which represents the four Welsh regions.
Cardiff Blues chairman Peter Thomas told ITV News he's 'forever optimistic' that the dispute between the rugby regions and the WRU will be resolved. He said that discussions are ongoing and it is important for the regions and the WRU to be united.
He said central contracts, retaining Welsh talent and increased funding were all issues under discussion.
Cardiff Blues chairman Peter Thomas has told ITV News he believes a deal for a six-year participation agreement between the WRU and regions will be signed within days.
The WRU will meet with regions tomorrow and Thomas is optimistic that a new agreement will be made over a number of outstanding points.
He says that he believes that any agreement should be signed before the EGM next week.
Cardiff Blues hooker Matthew Rees says next year's Rugby World Cup is a huge motivation for him after returning to full fitness after a battle with testicular cancer.
Rees has been sidelined for six months while undergoing treatment but returned during the Blues' win over Ulster at the Arms Park on Saturday.
Now the British Lion is looking for a strong end to this season to put himself back in the reckoning for Wales.
Wales hooker Matthew Rees tweeted his thanks to fans last night after playing his first game for the Cardiff Blues since undergoing treatment for cancer.
Thanks for all your kind messages great to back more importantly what a outstanding performance and result by the whole team!! #cardiffblues
Cardiff Blues have finalised a deal to keep centre and Vice Captain Gavin Evans at the region for a further two years.
29 year old Evans has become a regular fixture in the Blues side since making his debut in 2009 after joining from the Scarlets. In that time has made 86 appearances, scoring five tries along the way.
"It's fantastic to finalise my future and be able to look forward to the next two seasons at Blues,” said Evans.
"I had a frustrating start to the season with injuries and setbacks, but now it's about getting a run of games together in these closing months and helping the side look to climb the league table."
"It is an exciting time to be at Blues as we look to the future and so much hard work is going on behind the scenes to get it right."
Defending champions Leinster moved back to the top of the RaboDirect PRO12 table with their sixth successive victory, last night, over Cardiff.
Leinster ran in four tries to the hosts' three, with Jimmy Gopperth finishing with 14 points thanks to two penalties and four conversions.
Gareth Davies, Kristian Dacey and Dan Fish touched down for the Blues.